COMMON causes of failure in dealing with chronic otitis in dogs include not treating the animal for long enough, inadequate ear cleaning, failure to identify and treat otitis media or chronic pathological changes, and the failure to identify and control the primary causes of the otitis.
This was how Dr Anke Hendricks, lecturer in veterinary dermatology at the Royal Veterinary College, ended her presentation at the London Vet Show last month.
Speaking on “The nightmare of chronic otitis in the dog – what are the options?”, she spoke of the frustrations for all parties which were generated by the disease.
Dr Hendricks reviewed the predisposing factors which increased the risk of developing otitis externa, which worked in conjunction with other factors to cause disease.
These included conformation problems such as stenotic or hairy ear canals and pendulous pinnae; excessive moisture; excessive cerumen production; iatrogenic problems due to trauma from epilation or cotton buds and irritant topicals; obstructions such as neoplasms, nasopharyngeal polyps, granulomas or cysts; keratinisation disorders such as hypothyroidism or metabolic or nutritional problems; and glandular disorders such as ceruminal or sebaceous gland hyperplasia.
The speaker listed a number of points to be considered for the diagnosis of ear infections, noting that there was no reliable correlation between the nature of the discharge and the causative agent. Generally, the micro-organisms isolated in otitis media were those associated with otitis externa, although there could be differences in both species and sensitivity between the canal and the middle ear.
Otoscopy
Tympanic membrane was clearly visible by otoscopy in about 75% of normal ears but only in just over a quarter of ears with otitis externa; a satisfactory view could be expected in only about 30% of inflamed ears under anaesthesia.
Noting that ear canal stenosis could be expected in any case of chronic otitis, she recommended pre-treatment to reduce stenosis, using glucocorticoids (or ciclosporin) prior to diagnostic procedures under anaesthesia. Dr Hendricks added that an intact tympanic membrane did not rule out otitis media. She commented that in one study the tympanic membrane was intact in 73% of the ears with otitis media.
“For the approach to such cases it should be assumed that otitis media is present unless proven otherwise,” she said.
It was essential to diagnose all the primary, predisposing and pepertuating factors and the key goals of treatment were to clean the ears, eliminate infection and reverse chronic pathological changes.
Treatment options included surgical management but this could not be divorced from the medical necessity of fully investigating all the components to the disease if failure and disappointment were to be avoided. Surgery was indicated for tumours, polyps and irreversible stenosis where the disease failed to respond to aggressive medical management or where such management was not possible or wanted by the client. End stage ears would need a total ear canal ablation and lateral bulla osteotomy.
Dr Hendricks said that medical management could be surprisingly successful but required a compliant, educated and determined owner as well as a fairly compliant patient as an intense treatment plan of at least three months’ duration would have to be followed.
But even after appropriate steps had been taken to resolve the infection to prevent its recurrence, has the battle really been won, she asked?
Continued cleaning
Dr Hendricks recommended continuation of the ear cleaning regime, at gradually decreasing frequency, once the antibiotic/antifungal medication could be stopped.
In cases where primary disease and predisposing factors could not be controlled, a life-long regular ear cleaning regime with cleanser and disinfectant would be required to prevent recurrence.
In addition, vigilance by the owners was essential to detect any recurrence as quickly as possible so that it could be dealt with swiftly.
The reported prevalence of infectious otitis media in dogs with acute otitis externa is 16%, while in dogs with chronic, recurrent otitis externa, the reported prevalence is 55- 88.9%, Dr Hendricks said.
